This invention relates to a swing type hydraulic servoactuator. More particularly, this invention relates to a swing type hydraulic servo-actuator which faithfully responds even to a very fine rotary displacement of the input shaft and which permits easy control of the torque of the output shaft.
In recent years, there have been suggested many hydraulic servo-mechanisms adopting the common basic principle of an input shaft and an output shaft each being provided with an oil feeding passage and an oil discharge passage in such a way as to enable the apertures of the passages to be controlled by virtue of the relative rotary displacement between the two shafts and, consequently, permit the rotary motion of the input shaft to be transmitted to the output shaft (such as by U.S. Pat. Nos. 3,858,484 and 3,939,756, Japanese Patent Public Disclosure No. 48373/1975 and Japanese Utility Model Public Disclosure No. 4892/1976, for example).
In these servo-mechanisms of the prior art, however, even if a relative rotary displacement exists between the input shaft and the output shaft, the two shafts may possibly fail to rotate in unison unless the magnitude of the rotary displacement exceeds a certain value, i.e. unless the rotary displacement is large enough to provide communication between the oil feeding passages or between the oil discharge passages. Thus, with the conventional servo-mechanisms, it has been difficult to provide faithful control of fine rotary motion of the output shaft when the shaft is in the neighborhood of its neutral position.
Furthermore, the variation produced in the torque of the output shaft in response to even a very fine rotary displacement occurring between the input shaft and the output shaft is fairly large. This disadvantageous phenomenon has rendered stable control of the torque of the output shaft very difficult.
An object of the present invention is to provide a swing type hydraulic servo-actuator capable of easy control of a very fine rotary motion of the output shaft even when the shaft is in the neighborhood of its neutral position.
Another object of this invention is to provide a swing type hydraulic servo-actuator capable of controlling the output torque of the output shaft by virtue of the relative rotary displacement between the input and output shafts.
Still another object of the present invention is to provide a swing type hydraulic servo-actuator which possesses a simple structure and permits reduction in size.